Azzrushem, Guardian of the Crystal Depths

Legendary Resistance (3/Day). If Azzrushem fails a saving throw, he can choose to succeed instead.

Spider Climb. Azzrushem can climb on difficult surfaces, including up-side down on ceilings, without needing to make an agility check.

Tunnler.  Azzrushem can burrow through solid rock at half of its burrowing speed and can leave a 20-foot diameter tunnel in its wake.

Guardian of the Crystal Depths (3/Day). Azzrushem on his turn may create a dome of psionic energy around himself increasing his AC by two, and is immune to spells below 5th level until the start of his next turn.

Innate Spellcasting. Azzrushem spellcasting ability is Intelligence(spell save DC22). Azzrushem can innately cast the following spells, requiring no material components: 

At will: Dispel Magic, Detect Magic, Sending, Detect Thoughts, Telekinesis 

3/Day each: Psychic Lance, Dissident Whispers, Lightning Bolt

2/day each: Teleport, Feeble Mind, Hold Monster

1/day each: Prismatic Spray, Planeshift 

Magic Resistance.  Azzrushem has advantage on saving throws against spells or magical effects. 

Multiattack. Azzrushem makes one bite attack and two claw attacks. 

Bite. Melee Weapon Attack: +15 to hit, reach 15 ft., one target. Hit: 19 (2D10+8) piercing damage plus 11 (2D10) thunder damage.

Claw. Melee Weapon Attack: +15 to hit, reach 15ft., one target. Hit 15 (2D6+8) slashing damage. 

Debilitating Breath (Recharge 5-6).  Azzrushem exhales a pulse of high pitched, nearly in audible sound in a 90 foot cone. Each creature in that area must make a DC 23 Constitution saving throw. On a failed save, the creature takes 55 (10D10) thunder damage and is incapacitated until the end of its next turn. On a successful sace, the creature takes half as much damage and isn't incapacitated. 

Change Shape. Azzrushem magically transforms into a creature that is medium or small, while retaining its game statistics (other than its size). This transformation ends if the dragon is reduced to 0 hit points or uses a bonus action to end it. 

Psychic Step. Azzrushem magically teleports to an unoccupied space it can see within 60 feet of it. 

Counterspell, Opportunity Attack 

Azzrushem can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. Azzrushem regains spent legendary actions at the start of his turn.

Claw. Azzrushem makes one claw attack. 

Psionics (Cost 2 Actions). Azzrushem uses Psychic Step or Spellcasting

Telekinetic Fling (Cost 3 Actions). Azzrushem chooses one Medium or smaller object that isn't being worn or carried that it can see within 60 feet of it, and it magically hurls the object at a creature it can see within 60 feet of the object. The target must succeed on a DC 20 Dexterity saving throw or take 42 (12D6) bludgeoning damage.